Jumping ahead, let's assume that I've waited a month or two, called the hotel and they're happy, called the CC company and they're happy and then discussed it with my employer and I agree to pay the money back somehow. How does this rebate get managed? If it comes off my pay packet then I am effectively getting tax relief on an expense claim (less gross pay = less PAYE) which will presumably catch up with me eventually, but also a lower pension contribution that month. Will this get spotted if I get inspected by HMRC?

From the company's POV, if they simply take it off my next reimbursement for expenses then when they get audited won't that flag up and cause a headache, especially cross-quarters? My employer also has to undo any reclaim of VAT that they may have made, don't they? Any accountants out there got a suggestion?